autoprotolízise

Autoprotolysis is a chemical process where a compound undergoes proton transfer from one molecule to another molecule of the same compound. This reaction results in the formation of a cation and an anion. It is a specific type of autoionization, where the autoionization involves the transfer of a proton. This phenomenon is most commonly observed in protic solvents, which are liquids containing hydrogen atoms that are bonded to electronegative atoms like oxygen or nitrogen, making them capable of donating a proton.

A classic and well-known example of autoprotolysis is the self-ionization of water. In pure water, a small fraction of water molecules donate a proton to another water molecule, forming hydronium ions (H₃O⁺) and hydroxide ions (OH⁻). This equilibrium is represented by the equation 2H₂O ⇌ H₃O⁺ + OH⁻. The extent of autoprotolysis is quantified by the ion product constant, Kw, which is temperature-dependent.

Other substances also exhibit autoprotolysis. For instance, liquid ammonia (NH₃) undergoes autoprotolysis to form ammonium ions (NH₄⁺) and amide ions (NH₂⁻) according to the equilibrium 2NH₃ ⇌ NH₄⁺ + NH₂⁻. Similarly, liquid sulfuric acid (H₂SO₄) can undergo autoprotolysis to form hydronium ions and bisulfate ions (HSO₄⁻), with the simplified equilibrium 2H₂SO₄ ⇌ H₃SO₄⁺ + HSO₄⁻. The presence of ions from autoprotolysis means that even pure protic solvents possess some electrical conductivity. The strength of autoprotolysis varies significantly between different compounds and is influenced by factors such as temperature and molecular structure.